256839421 has 2 divisors, whose sum is σ = 256839422. Its totient is φ = 256839420.

The previous prime is 256839391. The next prime is 256839467. The reversal of 256839421 is 124938652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 236236900 + 20602521 = 15370^2 + 4539^2 .

It is a cyclic number.

It is not a de Polignac number, because 256839421 - 2⁵ = 256839389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256839481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128419710 + 128419711.

It is an arithmetic number, because the mean of its divisors is an integer number (128419711).

Almost surely, 2^256839421 is an apocalyptic number.

It is an amenable number.

256839421 is a deficient number, since it is larger than the sum of its proper divisors (1).

256839421 is an equidigital number, since it uses as much as digits as its factorization.

256839421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 103680, while the sum is 40.

The square root of 256839421 is about 16026.2104379045. The cubic root of 256839421 is about 635.6536728763.

The spelling of 256839421 in words is "two hundred fifty-six million, eight hundred thirty-nine thousand, four hundred twenty-one".